It is known, as described in U.S. Pat. Nos. 3,317,322, 3,761,276, etc., that chemical sensitization of the surface of internal latent image type silver halide grains comprising a central core of silver halide subjected to metal ion doping, chemical sensitization or a combination thereof and a chemically sensitized outer shell of silver halide covering at least light-sensitive sites of the central core (hereinafter these grains are referred to as "core/shell type grains") permits one to obtain a reversal image by direct reversal processing of the type where development is performed in the presence of a fogging agent or the elements is over-all light-exposed at development.
However, chemically sensitized nuclei prepared by the chemical sensitization of the surface of such core/shell type silver halide grains are poor with respect to stability with time and, therefore, when used after storage for a long period of time, give rise to the problems that there cannot be obtained a reversal image having a desired maximum density (D.sub.max), and the minimum density (D.sub.min) of the reversal image is increased.
Chemical sensitization of the surface of internal latent image type silver halide grains inevitably causes an increase in the formation of negative images. With conventional surface chemical sensitization methods, when surface chemical sensitization is performed to the extent that the D.sub.max of the reversal image obtained is satisfactory, the increase in the formation of the negative images is large, resulting in deterioration of reversal photographic characteristics, e.g., formation of false images at high illumination areas. Moreover, the D.sub.max values obtained by conventional surface chemical sensitization methods are not sufficiently large as compared with the D.sub.min values. As a result, the discrimination of the reversal image is insufficient and, at the same time, it is difficult to obtain a reversal image of high tone.
Furthermore, direct positive silver halide light-sensitive materials prepared using conventional internal latent image type silver halide photographic emulsions have poor low illumination reciprocity law failure characteristics, and it has been desired to improve such poor low illumination reciprocity law failure characteristics.